In recent years, the exhaust emission regulations for automobiles have been strengthened. In order to cope with this situation, exhaust gas purifying catalysts for purifying hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx), and the like in exhaust gases have been developed.
For example, Patent Literature 1 discloses a catalyst which contains palladium and praseodymium oxide and is capable of maintaining and exhibiting excellent oxygen storage capabilities even in a high temperature atmosphere of 900° C. or higher.
Patent Literature 2 discloses a catalyst in which palladium oxide (PdO) particles having an average particle diameter of 1 nm or more and 50 nm or less and rare-earth oxide particles having an average particle diameter of 1 nm or more and 50 nm or less are supported on a carrier. By this catalyst, the temperature at which Pd is precipitated by decomposition of PdO is increased, and grain growth of Pd is inhibited even in a high temperature environment of 900° C., and thus a deterioration in the catalyst activity is prevented.